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The biochemical oxygen demand (BOD) represents the amount of dissolved oxygen (DO) consumed by biological organisms when they decompose organic matter in water. The chemical oxygen demand (COD) is the amount of oxygen consumed when the water sample is chemically oxidised.
What is the BOD in water?
Biochemical oxygen demand, or BOD, is a chemical procedure for determining the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period.
What is BOD and COD in STP?
COD is closely related to BOD or Biochemical Oxygen Demand, the difference being that BOD is a test of the level of organic matter that can be biologically oxidised while COD is a test of the amount of organic matter that can be chemically oxidised.
Is high COD good or bad?
1.1 Chemical Oxygen Demand. COD is an indicative measurement of the amount of oxygen that can be consumed by reactions in a measured solution. COD detection can be used to easily quantify the amount of organics in water. The higher the COD value, the more serious the pollution of organic matter by water.
Which is greater ThOD or COD?
Explanation: ThOD mostly greater than COD. BODu = 0.9ThOD, ThOD > BOD.
Does BOD increase with temperature?
The amount of oxygen that can dissolve in water (DO) depends on temperature. Also, warmer water usually will have a higher BOD level than colder water. As water temperature increases, the rate of photosynthesis by algae and other plant life in the water also increases.
What is the limit of COD?
Parameter Unit Maximum permissible limit Chemical Oxygen Demand (COD) mg/l 120 Biochemical Oxygen Demand (BOD 5 ) mg/l 40 Chloride mg/l 1500 Sulphate mg/l 1500.
How do you reduce COD in wastewater?
You can reduce COD and BOD by adding hydrogen peroxide to the wastewater solution. The hydrogen peroxide will chemically attack the organics in the wastewater, degrading them and reducing the measured COD and BOD.
What is the COD value of drinking water?
The concentrations of COD observed in surface waters range from 20 mg/l O2 or less in unpolluted waters to greater than 200 mg/l O2 in waters receiving effluents. Industrial wastewaters may have COD values ranging from 100 mg/l O2 to 60,000 mg/ O2.
What causes high COD levels?
COD increases as the concentration of organic material increases. It also increases if inorganic compounds susceptible to oxidation by the oxidant (typically dichromate) are present. Water with high COD typically contains high levels of decaying plant matter, human waste, or industrial effluent.
What is BOD PPT?
Biological Oxygen Demand (BOD) is a measure of the oxygen used by microorganisms to decompose this waste. A large quantity of organic waste in the water supply, guarantees a large number bacteria present to decompose this waste.
How do you remove COD and BOD from water?
There are different options for Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) removal: A first option is biological purification where the polluting components are removed by means of bacteria. Sometimes, an alternative is the use of ultrafiltration to separate the polluting components.
Why is COD higher than BOD?
COD is normally higher than BOD because more organic compounds can be chemically oxidised than biologically oxidised. This includes chemicals toxic to biological life, which can make COD tests very useful when testing industrial sewage as they will not be captured by BOD testing.
Is high BOD in water good?
Higher BOD indicates more oxygen is required, which is less for oxygen-demanding species to feed on, and signifies lower water quality. Inversely, low BOD means less oxygen is being removed from water, so water is generally purer.
How COD is calculated?
Chemical oxygen demand, or COD, is a test that measures the amount of organic compounds in water. Consider the formula for COD calculation: (a – b) X C X 8,000 / the volume of the sample in mL. Let “a” represent the titrant used for your sample expressed in mL.
What is BOD explain it?
Biochemical oxygen demand (BOD) is the amount of dissolved oxygen (DO) needed (i.e. demanded) by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period.
What is BOD curve?
The Q-value curve for BOD used in calculating a water quality index2 illustrates the relationship between BOD and water quality—the higher the BOD, the lower the water quality, with 0 to 2 mg/L being associated with high water quality and values greater than 10 mg/L being associated with low water quality (refer to the
How is high COD wastewater treated?
COD Removal by Microbial Action Aerobic COD removal introduces microorganisms or bacteria that break down organic compounds present in wastewater into carbon dioxide and water in the presence of air. Aerobic COD removal is ideal for wastewater with COD < 3000 mg/L.
What happens if COD is high?
Higher COD levels mean a greater amount of oxidizable organic material in the sample, which will reduce dissolved oxygen (DO) levels. A reduction in DO can lead to anaerobic conditions, which is deleterious to higher aquatic life forms.
What is the difference between BOD and COD?
The main difference between BOD and COD is that BOD is the amount of oxygen which is consumed by bacteria while decomposing organic matter under aerobic conditions whereas COD is the amount of oxygen required for the chemical oxidation of total organic matter in water.
What causes COD in wastewater?
Background: Chemical oxygen demand (COD) is often used to measure organic matter in wastewater, treated effluent, and receiving waters. Residual food waste from bottles and cans, antifreeze, emulsified oils are all high in COD and are common sources of COD for industrial stormwater.
What increases BOD water?
BOD directly affects the amount of dissolved oxygen in rivers and streams. Sources of BOD include leaves and woody debris; dead plants and animals; animal manure; effluents from pulp and paper mills, wastewater treatment plants, feedlots, and food-processing plants; failing septic systems; and urban stormwater runoff.
What BOD and COD stands for?
BOD (biochemical oxygen demand) COD (chemical oxygen demand)
What is a good BOD level?
A BOD level of 1-2 ppm is considered very good. There will not be much organic waste present in the water supply. A water supply with a BOD level of 3-5 ppm is considered moderately clean.
